New SSL features for Nginx.

Brice Figureau brice+nginx at
Wed Jul 22 21:20:39 MSD 2009

On 22/07/09 14:16, Igor Sysoev wrote:
> On Wed, Jul 22, 2009 at 12:21:23PM +0200, Brice Figureau wrote:
>> Hi Igor,
>> On Wed, 2009-07-22 at 12:44 +0400, Igor Sysoev wrote:
>>> On Tue, Jul 21, 2009 at 08:02:05PM +0200, Brice Figureau wrote:
>>>> Hi,
>>>> For Puppet[1] Nginx deployement (that is using Nginx as a front-end 
>>>> load-balancers to puppetmasters[2]), I had to create the following two 
>>>> patches, to match Apache behaviour:
>>>>  * The first patch allows:
>>>>   + a new variant of ssl_client_verify: optional. In this mode, if the 
>>>> client sends a certificate it is verified, but if the client doesn't 
>>>> send a certificate, the connection is authorized too.
>>>>   + a new variable: $ssl_client_verify which contains, either NONE, 
>>>> SUCCESS or FAILURE depending on the verification status. It can be used 
>>>> to send information to the upstream about the client verification.
>>>>  * The second patch adds CRL support to the client certificate 
>>>> verification:
>>>>   ssl_crl /path/to/crl.pem;
>>>>  Nginx then verifies the client certificate hasn't been revoked in the 
>>>> given CRL before allowing the connection to proceed.
>>>> For access to the patches, please see my last blog article:
>>>> It would be great if those patches could be merged in the official Nginx 
>>>> source tree.
>>> Thank you, I have looked the patches, it was really surpise for me that
>>> OpenSSL 0.9.7 supports CRL. I read in old enough book "Network Security
>>> with OpenSSL" written when 0.9.7 was being developed, that OpenSSL has
>>> no built-in CRL support. 
>> Ah, ok. I based all my development on OpenSSL 0.9.8, since that's what
>> I'm building Nginx againt. And definitely there is CRL support.
>> Is OpenSSL 0.9.7 a strict dependency for Nginx?
> No. I think this code should be just "#ifdef'ed X509_V_FLAG_CRL_CHECK".

I'm OK with this. BTW, I checked and CRL support was added in 0.9.7.

>>> Then I have looked in Apache's mod_ssl sources and
>>> its CRL support seemed to me very heavy: mod_ssl does a lot of useless
>>> operations.
>> Which ones?
>> What I don't get is why they're doing the CRL verification themselves.
> Because mod_ssl were developed before 0.9.7.

Yes, I do think so. But it's error-prone and certainly less efficient.

>> I found this comment in the code:
>>      * OpenSSL provides the general mechanism to deal with CRLs but does
>> not
>>      * use them automatically when verifying certificates, so we do it
>>      * explicitly here. We will check the CRL for the currently checked
>>      * certificate, if there is such a CRL in the store.
>> This seems wrong to me, as I already tested, and it works fine at least
>> in version 0.9.8.
> Yes, this implementation. However, I made mistake: it's not too heavy as
> it seemed to me first time I have looked.
>>> I think that it's enough to store hash of only public key of
>>> all CRL certificates (including intermediate ones). 
>> Why reinvent the wheel?
>> The CRL is a standard thing (see RFC 3280), and basically this is a DER
>> encoded ASN1 structure containing the list of the revoked certificates
>> serial number, signed by the CA cert.
>>> Have you looked
>>> how CRL is implemented in OpenSSL ?
>> Yes, I did. It is pretty extensive, and matches RFC3280.
>> I'll fetch OpenSSL 0.9.7 to see if it supports or not CRL, but I'd be
>> suprised it wouldn't.

0.9.7 definitely supports CRL verification.

>> Thanks for reviewing the patch (at least the first one could be merged,
>> isn't it?).
> Probabaly, I will commit the patches in next 0.8.7.

Will you merge the CRL one (feel free to rewrite it if you prefer), too ?

Brice Figureau
My Blog:

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